Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1998-08-25
2001-01-16
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S020000, C353S037000, C349S009000
Reexamination Certificate
active
06174060
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a projection-type display apparatus that is preferably applied to a triple-plate type color projector using reflection-type spatial light modulating sections, and more particularly to an improvement for preventing deterioration of a projected picture or image and eliminating adverse influence of unnecessary polarized component as well as providing an arrangement of optical elements for downsizing the apparatus.
The triple-plate type color projector has a light source, such as a xenon lamp or a metal halide lamp, to generate white light. The white light is separated into three primary color beams. Each separated color beam is guided to a corresponding spatial light modulating section, such as a liquid crystal panel, to modulate each color beam in accordance with an image signal relating to a corresponding color. Thereafter, three modulated beams are combined to project the resultant composite light on a screen.
The color separating and light guiding system of this display apparatus is generally arranged in such a manner that the optical path of each separated color beam extending from the light source to a corresponding spatial light modulating section is identical in length with those of two other separated color beams. This arrangement is essentially important for obtaining a highly bright projection image as well as eliminating undesirable color shading.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical arrangement for downsizing the apparatus body of the triple-plate projection-type display apparatus that uses the reflection-type spatial light modulating sections.
Another object of the present invention is to provide an arrangement of polarized beam splitters used for selectively supplying specific polarized components to the reflection-type spatial light modulating sections, wherein adverse effects of unnecessary polarized components produced by the polarized beam splitters are effectively suppressed.
Another object of the present invention is to provide an arrangement of an illumination apparatus capable of suppressing the fluctuation of the illumination light caused by the convection of light source gas as well as providing bright illumination.
In order to accomplish the above and other related objects, the present invention provides a projection-type display apparatus comprising an illumination apparatus, a color separating/light guiding optics located at a predetermined deck, and a light modulating/color compositing/image projecting optics located at another deck. The illumination apparatus comprises a light source. The color separating/light guiding optics separates white color light emitted from the light source into three primary color beams and guides the separated primary color beams toward the light modulating/color compositing/image projecting optics. The light modulating/color compositing/image projecting optics comprises a cross-type dichroic prism with two reflection films crossing each other and having wavelength selectivity for selecting two of three primary colors, a projection lens disposed at an outgoing surface of the cross-type dichroic prism, polarized beam splitters having outgoing surfaces respectively facing to three incident surfaces of the cross-type dichroic prism and incident surfaces for receiving the separated primary color beams incoming from the color separating/light guiding optics, and the reflection-type spatial light modulating sections respectively facing to other surfaces opposing to the outgoing surfaces of the polarized beam splitters. A plane region occupied by the color separating/light guiding optics is entirely involved in a plane region occupied by the light modulating/color compositing/image projecting optics when seen from an up-and-down direction.
With this arrangement, the plane region occupied by the color separating/light guiding optics can be effectively reduced to a level comparable with that of the light modulating/color compositing/image projecting optics. This realizes a significant downsizing of the apparatus.
Preferably, the polarized beam splitters have polarizing films directed in predetermined directions in such a manner that the incident surfaces of the polarized beam splitters face toward the color separating/light guiding optics.
Preferably, the color separating/light guiding optics comprises two independent dichroic mirrors and a plurality of reflection mirrors.
Preferably, the color separating/light guiding optics guides first and second primary color beams along first and second optical paths identical in length and extending from the light source to corresponding polarized beam splitters facing to neighboring incident surfaces of the cross-type dichroic prism of the light modulating/color compositing/image projecting optics. The color separating/light guiding optics guides a third primary color beam along a third optical path serving as a detoured optical path longer than the first and second optical paths and extending from the light source to the corresponding polarized beam splitter across a dead space below the projection lens of the light modulating/color compositing/image projecting optics. And, at least one correcting lens is provided in the detoured third optical path to substantially equalize the optical path length of the third primary color beam with those of the first and second primary color beams.
Accordingly, the dead space is utilized for the detoured optical path of the color separating/light guiding optics for guiding one of the primary color beams to the corresponding polarized beam splitter. The detoured optical path provided a sufficient physical space for installing the required correcting lenses.
Preferably, an intermediate deck of a polarized light selecting optics is interposed between the two decks. The polarized light selecting optics comprises three polarized beam splitters facing to corresponding incident surfaces of respective polarized beam splitters of the light modulating/color compositing/image projecting optics. Each of the polarized beam splitters of the polarized light selecting optics allows one polarized component of the corresponding primary color beam to pass through and enter the corresponding polarized beam splitter of the light modulating/color compositing/image projecting optics and reflects the other polarized component in a direction different from the one polarized component.
Furthermore, the present invention proposes an arrangement of the polarized beam splitter located in the polarized light selecting optics. A reflection film is provided at a side surface of the polarized beam splitter for reflecting another polarized component having a polarization plane normal to the specific polarization plane.
With this arrangement, unnecessary polarized component returns to the light source without giving adverse effects to the component members.
Moreover, the present invention proposes an arrangement of the illumination apparatus. Preferably, the light source is a xenon lamp equipped with a convergence-type reflector and an illuminating device for unifying an illuminance distribution. The illuminating device may comprise a collimator lens and a pair of fly-eye lenses, and the collimator lens has a spherical aberration not smaller than 0.01 f. Alternatively, the illuminating device may comprise a light pipe having a rectangular hollow space defined by an aspect ratio of 3:4 and a diagonal aperture length of 5 to 10 mm, and the light pipe is located in the vicinity of a second focal point of the xenon lamp.
With this arrangement, it becomes possible to suppress the fluctuation of the illumination light caused by the convection of the xenon gas. The flicker is suppressed and the illuminance is improved.
REFERENCES:
patent: 4191456 (1980-03-01), Hong et al.
patent: 4702716 (1987-10-01), Roberts
patent: 4943154 (1990-07-01), Miyatake et al.
patent: 5365287 (1994-11-01), Vollmer et al.
patent: 5418583 (1995-05-01), Masumoto
patent: 5452128 (1995-09-01), Kimura
patent: 56264
Imaoka Hirofumi
Ishizaka Yasuo
Koyama Fujiko
Moriya Satoru
Suzuki Tetsuji
Anderson Kill & Olick P.C.
Dowling William
Victor Company of Japan Ltd.
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